Extensive grazing of semi-improved grassland to enhance faunal biodiversity
		Simon Mortimer, Ben Woodcock, Andrew Edwards, Clare Lawson, Alex Brook and Stephanie Harris Jerry Tallowin and Andrew Rook (IGER) Grassland spatial, temporal and architectural heterogeneity have major impacts on invertebrate abundance and diversity. However, our knowledge of the way in which canopy structure, patch size and patch dynamics influence invertebrate populations is limited, particularly for species-poor semi-improved neutral grasslands, which represent a major grassland resource in the UK. The role of livestock in creating and maintaining structural heterogeneity and driving patch dynamics in grasslands is well recognized This project provides insights into interactions between these variables and invertebrate abundance and diversity. This project will also provide some measure of the potential for biodiversity enhancement achievable simply through extensification of management on agricultural grasslands. OBJECTIVES To quantify the effects of differences in breed type (commercial vs. traditional beef cattle) and grazing intensity on plant community composition and structure To quantify the effects of differences in canopy structure, patch size and patch dynamics on invertebrate abundance and diversity To provide guidelines for the development of sustainable grazing management practices for the enhancement and maintenance of the invertebrate diversity of semi-improved grasslands. APPROACH Study site The experimental site was established early in 2002 on an area of semi-improved grassland (MG7b/ MG10a). The experimental site had received both inorganic nitrogen fertiliser and moderately intensive grazing for more than 10 years, creating a uniformly structured grass sward. Grazing treatments The experimental site has been fenced to create 9 paddocks of approximately 1.5 ha. The following three grazing treatments have been applied in three replicate blocks: MC: Moderate grazing intensity using a commercial breed (Charolais) LC: Lenient grazing intensity using a commercial breed (Charolais) LT: Lenient grazing intensity using a traditional breed (Red Devon) Sampling The relationship between grazing treatments, plant species composition and invertebrate assemblages is being examined through repeated sampling within permanently marked plots. The impact of the grazing treatments on canopy structure is studied using a number of destructive and non-destructive techniques. Drop discs record vegetation height using both grid and transect-based sampling regimes within the paddocks. The cover abundance of selected plant species, together with bryophytes and bare ground, are recorded at each sample point. RESULTS Data on vegetation composition and structure were analysed using K-means cluster analysis in order to define different patch types. Even after a few months of the grazing treatments, differences between treatments can be observed, with the MC paddocks characterised by extensive areas of short turf with isolated patches of Juncus effusus. The LT paddocks have taller turf and a different suite of patch types, whilst the LC paddocks are intermediate. Ongoing sampling will focus on quantifying: The change in the frequency of different patch types in response to the grazing treatments The size of different patch types and their spatial and temporal dynamics The invertebrate fauna associated with different patch types Research PartnerSponsor